This paper describes the development of a bee swarm algorithm for optimising the distribution of impact detection sensors on a composite plate. The algorithm was initially developed and tested on a travelling salesman problem, it was then adapted to solve the sensor placement problem using an artificial neural network to assess the fitness of sensor distributions. It performed well, managing to quickly find optimum distributions within a constrained set of neural network parameters. The algorithm was modified further, to optimise the neural network parameters alongside the sensor distributions and the range that the network parameters could take was substantially increased. This led to significant increases in accuracy. The algorithm showed itself to be a very effective tool in the sensor optimisation problem as well as demonstrating the benefits of thoroughly optimising the neural network parameters.

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This paper describes the development of a bee swarm algorithm for optimising the distribution of impact detection sensors on a composite plate. The algorithm was initially developed and tested on a travelling salesman problem, it was then adapted to solve the sensor placement problem using an artificial neural network to assess the fitness of sensor distributions. It performed well, managing to quickly find optimum distributions within a constrained set of neural network parameters. The algorithm was modified further, to optimise the neural network parameters alongside the sensor distributions and the range that the network parameters could take was substantially increased. This led to significant increases in accuracy. The algorithm showed itself to be a very effective tool in the sensor optimisation problem as well as demonstrating the benefits of thoroughly optimising the neural network parameters.Extension of the Optimised Virtual Fields Method to Estimate Viscoelastic Material Parameters from 3D Dynamic Displacement Fieldshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12126Extension of the Optimised Virtual Fields Method to Estimate Viscoelastic Material Parameters from 3D Dynamic Displacement FieldsN. Connesson, E. H. Clayton, P. V. Bayly, F. Pierron2015-02-06T18:49:57.64968-05:00doi:10.1111/str.12126John Wiley & Sons, Inc.10.1111/str.12126http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12126Full Papern/an/aAbstract

In vivo measurement of the mechanical properties of soft tissues is essential to provide necessary data in biomechanics and medicine (early cancer diagnosis, study of traumatic brain injuries, etc.). Imaging techniques such as magnetic resonance elastography can provide 3D displacement maps in the bulk and in vivo, from which, using inverse methods, it is then possible to identify some mechanical parameters of the tissues (stiffness, damping, etc.). The main difficulties in these inverse identification procedures consist in dealing with the pressure waves contained in the data and with the experimental noise perturbing the spatial derivatives required during the processing. The optimised virtual fields method (OVFM) (Comput. Mech.34, 2004, 439), designed to be robust to noise, presents natural and rigorous solution to deal with these problems. The OVFM has been adapted to identify material parameter maps from magnetic resonance elastography data consisting of 3D displacement fields in harmonically loaded soft materials. In this work, the method has been developed to identify elastic and viscoelastic models.

The OVFM sensitivity to spatial resolution and to noise has been studied by analysing 3D analytically simulated displacement data. This study evaluates and describes the OVFM identification performances: Different biases on the identified parameters are induced by the spatial resolution and experimental noise. The well-known identification problems in the case of quasi-incompressible materials also find a natural solution in the OVFM. Moreover, an a posteriori criterion to estimate the local identification quality is proposed. The identification results obtained on actual experiments are briefly presented.

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In vivo measurement of the mechanical properties of soft tissues is essential to provide necessary data in biomechanics and medicine (early cancer diagnosis, study of traumatic brain injuries, etc.). Imaging techniques such as magnetic resonance elastography can provide 3D displacement maps in the bulk and in vivo, from which, using inverse methods, it is then possible to identify some mechanical parameters of the tissues (stiffness, damping, etc.). The main difficulties in these inverse identification procedures consist in dealing with the pressure waves contained in the data and with the experimental noise perturbing the spatial derivatives required during the processing. The optimised virtual fields method (OVFM) (Comput. Mech. 34, 2004, 439), designed to be robust to noise, presents natural and rigorous solution to deal with these problems. The OVFM has been adapted to identify material parameter maps from magnetic resonance elastography data consisting of 3D displacement fields in harmonically loaded soft materials. In this work, the method has been developed to identify elastic and viscoelastic models.
The OVFM sensitivity to spatial resolution and to noise has been studied by analysing 3D analytically simulated displacement data. This study evaluates and describes the OVFM identification performances: Different biases on the identified parameters are induced by the spatial resolution and experimental noise. The well-known identification problems in the case of quasi-incompressible materials also find a natural solution in the OVFM. Moreover, an a posteriori criterion to estimate the local identification quality is proposed. The identification results obtained on actual experiments are briefly presented.The Effect of Size on the Splitting Strength of Cubic Concrete Membershttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12127The Effect of Size on the Splitting Strength of Cubic Concrete MembersR. Ince, M. Gör, M. E. Eren, K. E. Alyamaç2014-12-30T00:13:42.177655-05:00doi:10.1111/str.12127John Wiley & Sons, Inc.10.1111/str.12127http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12127Full Papern/an/aABSTRACT

In the study of concrete fractures, split-tension specimens, such as cylinders, cubes and diagonal cubes, are frequently preferred to beams. However, experimental investigations on concrete reveal that for the same specimen geometry, the nominal strength of specimen decreases with increasing specimen size. This phenomenon is named as the size effect in the fracture mechanics of concrete. Although nominal strength is also highly affected by the width of the distributed load in the split-tension cylinder and cube specimens, this effect can be negligible within the practical range of the load-distributed width in the diagonal cubes. However, the number of theoretical and experimental studies with diagonal split-tension specimens is limited. Besides, a size effect formula for estimating the split-tensile strength of the diagonal cube specimens has not been proposed. In this study, nine series of cube and diagonal cube specimens, with three different sizes but similar geometries, were tested under different load-distributed widths. The ultimate loads obtained from the test results are analysed by the modified size effect law. Subsequently, prediction formulas are proposed, and they are compared with historical test data from the split-cylinder specimens.

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In the study of concrete fractures, split-tension specimens, such as cylinders, cubes and diagonal cubes, are frequently preferred to beams. However, experimental investigations on concrete reveal that for the same specimen geometry, the nominal strength of specimen decreases with increasing specimen size. This phenomenon is named as the size effect in the fracture mechanics of concrete. Although nominal strength is also highly affected by the width of the distributed load in the split-tension cylinder and cube specimens, this effect can be negligible within the practical range of the load-distributed width in the diagonal cubes. However, the number of theoretical and experimental studies with diagonal split-tension specimens is limited. Besides, a size effect formula for estimating the split-tensile strength of the diagonal cube specimens has not been proposed. In this study, nine series of cube and diagonal cube specimens, with three different sizes but similar geometries, were tested under different load-distributed widths. The ultimate loads obtained from the test results are analysed by the modified size effect law. Subsequently, prediction formulas are proposed, and they are compared with historical test data from the split-cylinder specimens.Experimental Determination of the Mechanical Behaviour of Compacted Exfoliated Vermiculitehttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12125Experimental Determination of the Mechanical Behaviour of Compacted Exfoliated VermiculiteS. Belhouideg, M. Lagache2014-12-16T23:45:52.409635-05:00doi:10.1111/str.12125John Wiley & Sons, Inc.10.1111/str.12125http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12125Full Papern/an/aABSTRACT

A series of compacted exfoliated vermiculite samples were prepared, and their mechanical behaviour was experimentally studied. The vermiculite was first exfoliated and after compacted in order to obtain a material with good thermal and mechanical properties. The as-prepared samples have been tested under compressive loading. Some parameters effect was studied, as the porosity and the type of the compacted exfoliated vermiculite. The samples of this porous media display two steps for the stress–strain behaviour under uniaxial compressive loading, that is initial nonlinear deformation, strain-hardening ‘pseudo-platform’ stage.

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A series of compacted exfoliated vermiculite samples were prepared, and their mechanical behaviour was experimentally studied. The vermiculite was first exfoliated and after compacted in order to obtain a material with good thermal and mechanical properties. The as-prepared samples have been tested under compressive loading. Some parameters effect was studied, as the porosity and the type of the compacted exfoliated vermiculite. The samples of this porous media display two steps for the stress–strain behaviour under uniaxial compressive loading, that is initial nonlinear deformation, strain-hardening ‘pseudo-platform’ stage.Optimum Sensor Placement for Impact Location Using Trilaterationhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12123Optimum Sensor Placement for Impact Location Using TrilaterationM. De Stefano, M. Gherlone, M. Mattone, M. Di Sciuva, K. Worden2014-12-16T02:33:11.314245-05:00doi:10.1111/str.12123John Wiley & Sons, Inc.10.1111/str.12123http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12123Full Papern/an/aABSTRACT

A key problem associated with structural health monitoring (SHM) is the placement of sensors upon a structure to detect the existence, location, and the extent of any damage. Because input data coming from the sensors are groups of measurements, it is arguable that the most widely used approach to SHM nowadays is to consider it as a statistical pattern recognition problem. Artificial neural networks have made a great impact on pattern recognition practice. A problem associated with this monitoring strategy is to find a good compromise between the quality of information achieved by the sensor network, increasing with the sensor density, and the need to keep the minimum weight and instrumentation cost. Thus, the number of sensors must be kept under control, and a search of the optimal location of such sensors needs to be performed.

All these aspects have been taken into account in the present work, dealing with the problem of optimum sensor placement for impact location on a multilayered composite structure.

Multilayered composite structures may suffer particularly relevant trauma when subject to low-velocity impacts, as they may produce non-visible or barely visible damage on the structure surface, while remarkable subsurface delaminations may be present. Such hidden damage, when remaining undetected, may grow to catastrophic failure. To overcome this issue, a neural network approach has been used here to predict the impact locations on a composite panel from time-dependent data recorded on a set of surface-mounted piezoelectric sensors during an experimental impact test. A genetic algorithm has been used to find the optimal sensor layout that minimised the error in predicting the impact location. A new approach, based on trilateration, is discussed and compared with the traditional one and is shown to provide the same degree of accuracy at reduced computational cost.

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A key problem associated with structural health monitoring (SHM) is the placement of sensors upon a structure to detect the existence, location, and the extent of any damage. Because input data coming from the sensors are groups of measurements, it is arguable that the most widely used approach to SHM nowadays is to consider it as a statistical pattern recognition problem. Artificial neural networks have made a great impact on pattern recognition practice. A problem associated with this monitoring strategy is to find a good compromise between the quality of information achieved by the sensor network, increasing with the sensor density, and the need to keep the minimum weight and instrumentation cost. Thus, the number of sensors must be kept under control, and a search of the optimal location of such sensors needs to be performed.
All these aspects have been taken into account in the present work, dealing with the problem of optimum sensor placement for impact location on a multilayered composite structure.
Multilayered composite structures may suffer particularly relevant trauma when subject to low-velocity impacts, as they may produce non-visible or barely visible damage on the structure surface, while remarkable subsurface delaminations may be present. Such hidden damage, when remaining undetected, may grow to catastrophic failure. To overcome this issue, a neural network approach has been used here to predict the impact locations on a composite panel from time-dependent data recorded on a set of surface-mounted piezoelectric sensors during an experimental impact test. A genetic algorithm has been used to find the optimal sensor layout that minimised the error in predicting the impact location. A new approach, based on trilateration, is discussed and compared with the traditional one and is shown to provide the same degree of accuracy at reduced computational cost.Issue Informationhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12107Issue Information2015-01-27T16:12:06.824806-05:00doi:10.1111/str.12107John Wiley & Sons, Inc.10.1111/str.12107http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12107Issue Informationiii

No abstract is available for this article.

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No abstract is available for this article.50th Anniversary Article: Seeing Stresses through the Thermoelastic Lens—A Retrospective and Prospective from an Australian Viewpointhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.1211650th Anniversary Article: Seeing Stresses through the Thermoelastic Lens—A Retrospective and Prospective from an Australian ViewpointA. K. Wong, N. Rajic, Q. Nguyen2014-11-21T00:42:23.834177-05:00doi:10.1111/str.12116John Wiley & Sons, Inc.10.1111/str.12116http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12116Full Paper115Abstract

Thermoelastic stress analysis (TSA) has been around for the past 30 years, but to date, it is still a very much underrated and under-utilised experimental technique. Although there are devoted groups of practitioners in some industries, this technology is not well known within the aerospace sector. In contrast, the Aerospace Division of the Defence Science and Technology Organisation (DSTO) in Australia has been in the forefront of this technology for some time, achieving many pioneering feats. This paper gives a brief introduction to the development of this technology from a historical perspective, then focuses on a number of innovations that have stemmed from DSTO, including the development and application of the world's first focal plane array based TSA system and, more recently, the development of small and robust microbolometer based systems. For the latter, it is shown that despite nominally poorer temperature sensitivities, they make ideal TSA devices and can in some cases outperform their much more expensive photon detector counterparts. Because of this, together with the enormous practical advantages of microbolometers, the future of TSA is shown to be brighter than ever. Specifically, it is argued that such TSA systems can play a major role in the pervasive and persistent surveillance of full scale fatigue testing of aircraft structures. By detecting both design and developing faults early, it can effectively relieve cost and schedule penalties that are often associated with unanticipated failures. To realise this capability, integration of this technology with autonomous systems will be important, and some preliminary but promising results from a technology demonstrator program are presented.

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Thermoelastic stress analysis (TSA) has been around for the past 30 years, but to date, it is still a very much underrated and under-utilised experimental technique. Although there are devoted groups of practitioners in some industries, this technology is not well known within the aerospace sector. In contrast, the Aerospace Division of the Defence Science and Technology Organisation (DSTO) in Australia has been in the forefront of this technology for some time, achieving many pioneering feats. This paper gives a brief introduction to the development of this technology from a historical perspective, then focuses on a number of innovations that have stemmed from DSTO, including the development and application of the world's first focal plane array based TSA system and, more recently, the development of small and robust microbolometer based systems. For the latter, it is shown that despite nominally poorer temperature sensitivities, they make ideal TSA devices and can in some cases outperform their much more expensive photon detector counterparts. Because of this, together with the enormous practical advantages of microbolometers, the future of TSA is shown to be brighter than ever. Specifically, it is argued that such TSA systems can play a major role in the pervasive and persistent surveillance of full scale fatigue testing of aircraft structures. By detecting both design and developing faults early, it can effectively relieve cost and schedule penalties that are often associated with unanticipated failures. To realise this capability, integration of this technology with autonomous systems will be important, and some preliminary but promising results from a technology demonstrator program are presented.50th Anniversary Article: Multiaxial Fatigue Testing of Composites: From the Pioneers to Future Directionshttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.1212450th Anniversary Article: Multiaxial Fatigue Testing of Composites: From the Pioneers to Future DirectionsM. Quaresimin2014-12-29T23:56:45.127326-05:00doi:10.1111/str.12124John Wiley & Sons, Inc.10.1111/str.12124http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12124Full Paper1629Abstract

This paper presents an overview on the experimental investigation of the response of composite materials under multiaxial cyclic loading, starting from the pioneering works in the early 1970s to arrive to the research activities run in these days by the scientific community and concluding with the areas still open. The experimental techniques and sample geometries are compared, illustrating advantages and drawbacks of each solution, also with reference to the outcomes of the research. The influence of the main design parameters are illustrated, taking advantage of experimental results from the extensive investigation carried out in the last years at the University of Padova. Needs of future research are eventually addressed.

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This paper presents an overview on the experimental investigation of the response of composite materials under multiaxial cyclic loading, starting from the pioneering works in the early 1970s to arrive to the research activities run in these days by the scientific community and concluding with the areas still open. The experimental techniques and sample geometries are compared, illustrating advantages and drawbacks of each solution, also with reference to the outcomes of the research. The influence of the main design parameters are illustrated, taking advantage of experimental results from the extensive investigation carried out in the last years at the University of Padova. Needs of future research are eventually addressed.Modal Pursuit to Detect Large Displacements and Strain Fields by Digital Image Correlationhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12102Modal Pursuit to Detect Large Displacements and Strain Fields by Digital Image CorrelationP. Salvini, V. Lux, E. Marotta2014-08-21T22:58:44.86963-05:00doi:10.1111/str.12102John Wiley & Sons, Inc.10.1111/str.12102http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12102Full Paper3042Abstract

Digital image correlation offers a useful approach to resolve displacements and strains by picture comparisons. However, many of the several methods proposed in the past suffer the occurrence of large displacements between the two compared pictures. The modal pursuit approach here introduced intends giving a possible strategy to prevent this limitation. The main advantage is that the method uses a global approach for the solution strategy. The procedure uses a displacement basis that derives from a modal analysis on a membrane structure whose shape is the same as the image region under investigation. The modes are introduced a little at a time so that the procedure is facilitated to converge, even when only two pictures (undeformed and final state) are used for the matching.

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Digital image correlation offers a useful approach to resolve displacements and strains by picture comparisons. However, many of the several methods proposed in the past suffer the occurrence of large displacements between the two compared pictures. The modal pursuit approach here introduced intends giving a possible strategy to prevent this limitation. The main advantage is that the method uses a global approach for the solution strategy. The procedure uses a displacement basis that derives from a modal analysis on a membrane structure whose shape is the same as the image region under investigation. The modes are introduced a little at a time so that the procedure is facilitated to converge, even when only two pictures (undeformed and final state) are used for the matching.Experimental Study and Numerical Modelling of Creep and Stress Relaxation of Dielectric Elastomershttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12117Experimental Study and Numerical Modelling of Creep and Stress Relaxation of Dielectric ElastomersR. Sahu, K. Patra, J. Szpunar2014-10-22T11:08:39.51261-05:00doi:10.1111/str.12117John Wiley & Sons, Inc.10.1111/str.12117http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12117Full Paper4354Abstract

Dielectric elastomers (DEs) are gaining acceptance as potential actuator materials because of their exhibition of a large amount of deformation when stimulated by electrostatic forces. However, time-dependent behaviour such as creep and stress relaxation still pose a great challenge for the design, modelling and control of the DE-based actuators. In this work, attempts are made for experimental estimation and modelling of creep and relaxation properties of one of the most widely used dielectric acrylic elastomers, VHB 4910. Experimental investigation shows that the material possesses strong time-dependent creep and stress relaxation. It has been shown that creep and stress relaxation characteristics vary with the holding stress and holding strain respectively. Creep and stress relaxation properties are also shown to depend on the number of cycles in the case of cyclic loading. Results also show that Findley's power law can successfully model the creep and stress relaxation behaviour of the VHB 4910 elastomer.

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Dielectric elastomers (DEs) are gaining acceptance as potential actuator materials because of their exhibition of a large amount of deformation when stimulated by electrostatic forces. However, time-dependent behaviour such as creep and stress relaxation still pose a great challenge for the design, modelling and control of the DE-based actuators. In this work, attempts are made for experimental estimation and modelling of creep and relaxation properties of one of the most widely used dielectric acrylic elastomers, VHB 4910. Experimental investigation shows that the material possesses strong time-dependent creep and stress relaxation. It has been shown that creep and stress relaxation characteristics vary with the holding stress and holding strain respectively. Creep and stress relaxation properties are also shown to depend on the number of cycles in the case of cyclic loading. Results also show that Findley's power law can successfully model the creep and stress relaxation behaviour of the VHB 4910 elastomer.Towards Eliminating the Displacement Bias Due to Out-Of-Plane Motion in 2D Inverse Problems: A Case of General Rigid-Body Motionhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12120Towards Eliminating the Displacement Bias Due to Out-Of-Plane Motion in 2D Inverse Problems: A Case of General Rigid-Body MotionM. Z. Siddiqui2014-11-21T00:54:04.466285-05:00doi:10.1111/str.12120John Wiley & Sons, Inc.10.1111/str.12120http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12120Full Paper5570Abstract

This article reports an important development related to the inverse characterization of material constitutive parameters using 2D optical displacement field measurements. The out-of-plane motion of the specimen, which has traditionally been considered detrimental to the accuracy of these experiments, is generally of two types: (a) a global out-of-plane rigid-body motion of the specimen relative to the camera and (b) out-of-plane deformations resulting from material heterogeneity or out-of-plane loads. In an earlier article, we proposed to partially relax the condition of no out-of-plane motion by allowing for (b) in 2D inverse procedures, in the context of finite element update method, and introduced a compensation strategy by redefining the cost function on the object plane of the acquisition system. The experimental errors due to (a) were assumed negligible. Here, we propose that the global rigid-body motion (a) may also be recovered within the inverse procedures, hence completely waiving the condition of strictly in-plane displacements for inverse problems. The recovery is achieved by identifying and including the possible modes of global rigid-body motion within the cost function together with careful selection of test configuration. The effects of individual rigid-body modes on the computed displacement fields are studied in detail and utilized as a guideline for selection of test configuration. The approach is fully demonstrated and validated by simulated as well as real experiments for determining elastic constants of isotropic and orthotropic materials using different experimental setups. Effects of improving the optimization routine, for cost function minimization, and experimental noise are also presented.

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This article reports an important development related to the inverse characterization of material constitutive parameters using 2D optical displacement field measurements. The out-of-plane motion of the specimen, which has traditionally been considered detrimental to the accuracy of these experiments, is generally of two types: (a) a global out-of-plane rigid-body motion of the specimen relative to the camera and (b) out-of-plane deformations resulting from material heterogeneity or out-of-plane loads. In an earlier article, we proposed to partially relax the condition of no out-of-plane motion by allowing for (b) in 2D inverse procedures, in the context of finite element update method, and introduced a compensation strategy by redefining the cost function on the object plane of the acquisition system. The experimental errors due to (a) were assumed negligible. Here, we propose that the global rigid-body motion (a) may also be recovered within the inverse procedures, hence completely waiving the condition of strictly in-plane displacements for inverse problems. The recovery is achieved by identifying and including the possible modes of global rigid-body motion within the cost function together with careful selection of test configuration. The effects of individual rigid-body modes on the computed displacement fields are studied in detail and utilized as a guideline for selection of test configuration. The approach is fully demonstrated and validated by simulated as well as real experiments for determining elastic constants of isotropic and orthotropic materials using different experimental setups. Effects of improving the optimization routine, for cost function minimization, and experimental noise are also presented.Strain Profiling of a Ferritic-Martensitic Stainless Steel Sheet — Comparing Synchrotron with Conventional X-Ray Diffractionhttp://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12121Strain Profiling of a Ferritic-Martensitic Stainless Steel Sheet — Comparing Synchrotron with Conventional X-Ray DiffractionC.-O. A. Olsson, M. Boström, T. Buslaps, A. Steuwer2014-12-28T19:41:17.249976-05:00doi:10.1111/str.12121John Wiley & Sons, Inc.10.1111/str.12121http://onlinelibrary.wiley.com/resolve/doi?DOI=10.1111%2Fstr.12121Full Paper7177Abstract

To improve the fatigue resistance of stainless steel sheet, it is a common practice to induce compressive residual stress in the surface through shot-peening or tumbling. Stress depth profiles obtained by tumbling of thin stainless steel tensile rods were analysed using laboratory and synchrotron X-Ray Diffraction (XRD). Both the non-destructive synchrotron and the laboratory XRD etch-depth profile gave similar results: a residual stress profile decaying over a depth not exceeding 50 µm into the material.

Eleven wool and silk historic textiles and two modern artist's canvases were examined to determine their water vapour adsorption, moisture dimensional response and tensile behaviour. All the textiles showed a similar general pattern of moisture response. A rise in ambient relative humidity (RH) from dry conditions produced expansion of a textile until a certain critical RH level after which a contraction occurred to a greater or lesser degree depending on the yarn crimp and the weave geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for wool and silk textiles, respectively. The largest shrinkage of 0.8% at high RH range was experienced by a modern linen canvas. Two potential damage mechanisms related to the moisture response of the textiles—stress building as a result of shrinkage of the textile restrained in its dimensional response and the fretting fatigue when yarns move with friction one against another—were found insignificant in typical textile display environments unless the textiles are severely degraded or excessively strained in their mounting.

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Eleven wool and silk historic textiles and two modern artist's canvases were examined to determine their water vapour adsorption, moisture dimensional response and tensile behaviour. All the textiles showed a similar general pattern of moisture response. A rise in ambient relative humidity (RH) from dry conditions produced expansion of a textile until a certain critical RH level after which a contraction occurred to a greater or lesser degree depending on the yarn crimp and the weave geometry. The largest expansion recorded between the dry state and 80% RH was 1.2 and 0.9% for wool and silk textiles, respectively. The largest shrinkage of 0.8% at high RH range was experienced by a modern linen canvas. Two potential damage mechanisms related to the moisture response of the textiles—stress building as a result of shrinkage of the textile restrained in its dimensional response and the fretting fatigue when yarns move with friction one against another—were found insignificant in typical textile display environments unless the textiles are severely degraded or excessively strained in their mounting.